MESOSCALE DISCUSSION 0518
   NWS STORM PREDICTION CENTER NORMAN OK
   0123 PM CDT FRI APR 22 2011
   
   AREAS AFFECTED...CNTRL/ERN OK...FAR WRN AR...N-CNTRL/NERN TX
   
   CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 
   
   VALID 221823Z - 222000Z
   
   PORTIONS OF CNTRL/ERN OK...FAR WRN AR...AND N-CNTRL/NERN TX ARE
   BEING MONITORED FOR THUNDERSTORM DEVELOPMENT AND INCREASING SVR
   WEATHER THREAT. TORNADO WATCH WILL LIKELY BE NEEDED DURING THE NEXT
   FEW HOURS.
   
   EARLY AFTERNOON SURFACE ANALYSIS SHOWS AN AREA OF LOW PRESSURE
   MOVING E-NEWD ACROSS SERN KS...WITH A COLD FRONT TRAILING SWWD INTO
   SWRN OK...AND A DRYLINE EXTENDING S-SW FROM CNTRL OK INTO N-CNTRL
   TX. STRONG SURFACE HEATING AND STEEPENING LOW-LEVEL LAPSE RATES ARE
   DEVELOPING NEWD ALONG THE COLD FRONT/DRYLINE...AIDING IN BOUNDARY
   LAYER DESTABILIZATION. MEANWHILE...EXPANSIVE AREA OF MID 60S F
   DEWPOINTS RESIDE ACROSS THE WARM SECTOR BENEATH A PLUME OF STEEP
   MIDLEVEL LAPSE RATES...RESULTING IN STRONG INSTABILITY /MLCAPE
   VALUES AOA 2500 J PER KG/ ALONG/AHEAD OF THE SURFACE BOUNDARIES. 
   
   VIS SATELLITE IMAGERY AT 18Z SHOWS ENHANCED CUMULUS GROWTH OVER
   S-CNTRL OK...WHICH IS COINCIDENT WITH THE LOCATION OF RAPID
   THUNDERSTORM DEVELOPMENT IN 3KM HRRR OCCURRING BY 19-20Z. GIVEN
   THESE TRENDS...CONFIDENCE IS INCREASING THAT CONVECTIVE INITIATION
   WILL TAKE PLACE OVER PORTIONS OF CNTRL/ERN OK AND PERHAPS N-CNTRL TX
   DURING THE NEXT FEW HOURS. THOUGH DEEP LAYER SHEAR IS SOMEWHAT
   MARGINAL /EFFECTIVE BULK SHEAR FROM 35-45 KT/...THE STRONG
   INSTABILITY/STEEP MIDLEVEL LAPSE RATES SHOULD LEAD TO RAPID
   THUNDERSTORM INTENSIFICATION AND POSSIBLE SUPERCELL DEVELOPMENT
   POSING A THREAT FOR VERY LARGE HAIL. IN ADDITION...THE DEGREE OF
   INSTABILITY COMBINED WITH SUFFICIENT LOW-LEVEL SHEAR PROFILES /0-1
   KM SRH IN EXCESS OF 150 M2 S-2/ SUGGESTS THAT A TORNADO WATCH WILL
   NEED TO BE CONSIDERED.
   
   ..GARNER.. 04/22/2011
   
   
   ATTN...WFO...LZK...SGF...SHV...TSA...FWD...OUN...SJT...
   
   LAT...LON   33339941 35519751 36939564 36929417 34929420 33179505
               32559780 32659921 33339941